The current practice in protective fabrics is nearly universal in its use of continuous filament fiber for ballistic, spike and knife protection. Yarns of the continuous filament type in para-arimid, ultra high molecular weight polyethylene and PBO are all in common use in woven webs and laminated webs. The range of deniers in these products typically runs from 200 d to 1500 d (denier). These webs are used in multi-layer soft panel assembly to provide protection to the users. Types of garments include vests, neck, groin, leg and arm protection as well as other protective equipment.
The use of soft fabric based protective systems are based on the progressive reduction of penetrator energy. The ballistic case is typical. The energy of high velocity bullets is reduced in a progressive manner. Each layer in a soft ballistic panel is deflected by the ballistic impact. As each layer is displaced and reaches it tensile limit the energy of the ballistic impact is reduced. The basic relationship of force times distance (F×D) governs the reduction of ballistic energy performed by a soft panel. It is useful to think of this process as a series of force peaks as each fabric layer is deflected and penetrated.
The design of soft ballistic panels is based on this layered form of protection. The more layers that are used for a given weight of fiber, the higher the ballistic protection. In this way a soft, multi-layer panel that is properly supported, can absorb the energy of even non-deformable projectiles.
In a notable exception to the continuous filament fiber art, the inventor has developed the first staple based protective fabrics offering equivalent levels of spike protection. Application Ser. Nos. 09/943,744 and 09/943,749, both filed Aug. 30, 2001, are incorporated herein by reference.
The capital equipment needed to produce high strength, continuous filament fibers is expensive. The linear quantity requirement for a fabric using lower denier, smaller diameter filament fibers is proportionally higher than for using higher denier filament fibers, since it is made on the same machinery. The cost and availability of fine denier continuous filament fiber fabrics is therefore seriously affected.
What is needed is a less costly composition of high strength fibers, and less dependence on very fine or smaller denier continuous filament fibers; in short, a new fabric design that will provide generally equivalent performance with regard to weight, yarn stability, and penetration protection, as do the present low denier, continuous filament fiber fabrics of the prior art.